The present invention generally relates to power hand tools, and more particularly to portable circular saws.
Portable circular saws are in widespread use for cutting workpieces such as lumber, vinyl siding, etc. Examples of such circular saws are those produced under the Skil brand by the Robert Bosch Tool Corporation of Chicago, Ill. These circular saws generally include a rotary blade assembly and a motorized drive unit disposed within a housing, a single handle disposed on the housing, and a base or foot that rides on the workpiece during cutting operations.
When using circular saws, it is frequently desired to make saw blade adjustments for controlling particular aspects of a cut. For example, U.S. Pat. No. 4,856,394 to Clowers discloses a circular saw with an assembly (see FIGS. 2 and 5) for adjusting a depth of cut by controlling the extent to which a saw blade moved by pivoting action of the housing is positioned below a base or shoe which supports the circular saw on a workpiece. The housing includes a locking means, which lockably engages a plate via a locking stud extending though the housing. The circular saw also includes a locking nut that is rotatable and lockable against the plate by means of a locking handle that fixes the housing relative to the shoe in a plurality of continuous positions.
It is also known to provide a portable circular saw with a bevel angle adjustment mechanism for adjusting a bevel angle of cut. One example of such a circular saw disclosed by U.S. Pat. No. 6,202,311 to Nickels, Jr. discloses a base and a saw blade arranged so that a bevel angle is adjustable relative to the base (see FIGS. 1 and 2). A mounting bracket is attached to the base for relative pivotable movement about an axis, which enables adjustment of the bevel angle of cut.
Another known circular saw having a bevel angle adjustment is disclosed in U.S. Pat. No. 5,452,515 to Schilling and includes a base plate, a saw blade arranged so that a bevel angle is adjustable relative to the base plate, and a clamping block. The clamping block is supported by the base plate and provided with a turning guide slot. In addition, the clamping block also has a plurality of arresting pockets arranged along the turning guide slot. A clamping screw extends through the turning guide slot and a supporting arm and carries at least one axially spring-biased displaceable arresting sleeve which can be positioned in one of the arresting pockets. Another known arrangement for adjusting a bevel angle includes a spring-loaded ball that can engage spherically-shaped recesses positioned on a mounting bracket.
A desirable saw blade depth mechanism and/or bevel angle adjustment mechanism provides for convenient, easy and speedy manipulation to set the desired saw blade depth and/or bevel angle. In some applications, an operator may need to frequently change the saw blade depth and/or bevel angle setting. If it is difficult to easily make an adjustment of the depth of cut or bevel angle, such difficulty can make a significant difference in operating efficiency. Two significant aspects of a saw blade depth mechanism and/or bevel angle adjustment mechanism are the ease of effecting adjusting movements of the mechanism, and the accuracy and ability of a user to consistently set desired saw blade depths and/or bevel angles.
Prior known arrangements for adjusting the depth of a saw blade and/or adjusting its bevel angle involved locating a saw blade relative to a base at different depths, or one or more predetermined bevel angles. However, such prior known arrangements are not without their drawbacks. For example, many known arrangements are awkward to use because the user must set a single lock while simultaneously maintaining the saw at a desired saw blade depth and/or bevel angle setting. This often results in discrepancies in depths of saw blade cuts and/or angles of cut, especially for common cutting angles, since the depth and/or angle of the saw blade are user dependent. Additionally, known bevel angle adjustment mechanisms, including those having a spring-loaded ball, often tend to become clogged due to wood sap, sawdust, and other debris accumulating on the adjustment mechanism. Accordingly, it is desirable to have a saw blade depth mechanism and a bevel angle adjustment mechanism that provide self-cleaning action, are easy to use, and provide accurate saw blade depth settings and bevel angle of cut settings.